Vocal Fold Augmentation with Beta Glucan Hydrogel Cross-Linked by γ Irradiation for Enhanced Duration of Effect: In Vivo Animal Study

This study explored a novel strategy to restore the vocal gap by using cross-linked β-glucan hydrogel by γ-irradiation. An aqueous solution of 5 wt% β-glucan was prepared and cross-linked using (60)Co γ irradiation. Ten nude mice were injected with 0.8 mL of irradiated β-glucan on the left back and the same volume of nonirradiated β-glucan on the right back for comparison. The mice were sacrificed at 1 and 2 weeks after injection and histological evaluations were performed. Irradiated β-glucan demonstrated a significantly larger volume than nonirradiated β-glucan in the back of nude mice with less inflammatory reaction. After unilateral recurrent laryngeal nerve section in New Zealand White rabbits, irradiated and nonirradiated β-glucan were injected into paralyzed vocal folds. Irradiated β-glucan remained at the paralyzed vocal fold without definite inflammatory signs on endoscopy. High-speed recordings of vocal fold vibration showed decreased vocal gap in irradiated group compared to nonirradiated group. Histologically, the laryngeal epithelium and lamina propria remained intact, without inflammatory cell infiltration. Our newly developed injection material, irradiated β-glucan, showed excellent biocompatibility and remained longer than nonirradiated β-glucan in vivo, suggesting irradiated hydrogels as a new therapeutic approach that may be useful for the long-term treatment of vocal fold palsy.